なぜはこをあけたの。

why; how

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

sea cucumber (Holothuroidea spp.)

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

to raise; to elevate; to do up (one's hair); to fly (a kite, etc.); to launch (fireworks, etc.); to surface (a submarine, etc.); to land (a boat); to deep-fry; to show someone (into a room); to summon (for geishas, etc.); to send someone (away); to enrol (one's child in school); to enroll; to increase (price, quality, status, etc.); to develop (talent, skill); to improve; to make (a loud sound); to raise (one's voice); to earn (something desirable); to praise; to give (an example, etc.); to cite; to summon up (all of one's energy, etc.); to arrest; to nominate; to give; to offer up (incense, a prayer, etc.) to the gods (or Buddha, etc.); to bear (a child); to conduct (a ceremony, esp. a wedding); (of the tide) to come in; to vomit; to do for (the sake of someone else); to complete ...; to humbly do ...

indicates possessive; nominalizes verbs and adjectives; substitutes for "ga" in subordinate phrases; (at sentence-end, falling tone) indicates a confident conclusion; (at sentence-end) indicates emotional emphasis; (at sentence-end, rising tone) indicates question